The effect of high energy intake on microbial protein production and renal urea kinetics was studied in Corriedale sheep by the urinary allantoin method and renal functional tests. High energy diet increased microbial protein production (6.61±0.90 vs 4.30±0.60 g/d in normal energy diet, P<0.05). The efficiency of N utilization by rumen microbes tended to improve (19.8±4.2 vs 16.8±1.9 g microbial N/kg DOMR, NS). A reduction in fractional excretion of urea and a tendency to decrease of urinary urea elimination were also observed. This renal urea sparing reduced N losses, contributing to the blood urea pool available for rumen recycling.